1. Field of the Invention
The present invention relates to a water-based ink set for ink-jet recording suitable for reducing graininess in a low density printed part and for extending a color reproduction range. The present invention also relates to an ink-jet recording method using this water-based ink set for ink-jet recording.
2. Description of the Related Art
When a color image is expressed by an ink-jet recording method, a three color ink set has been generally used, composed of a yellow ink (Y), a magenta ink (M) and a cyan ink (C). Moreover, a four-color ink set has also been used in which a black ink (K) is further added to the standard three-color ink set.
Generally, in an ink-jet recording method, the gradation of an image is controlled by adjusting the density of dots formed by ejecting ink onto a recording material. However, when the gradation is controlled by such a method, the dot density decreases in a low density printed part. Relative to this, the individual dots become easily discernable to the eye, thereby causing the image to be grainy.
In view of the above, a method has been proposed in which two or more inks are employed as a cyan ink (Japanese Patent Application Laid-Open No. Hei 1-95093). In this method, these inks have different dye concentrations and are composed of different kinds of dyes. In addition, a dye which is excellent in vividness but inferior in light fastness is employed as a dark color ink, and a dye which is excellent in light fastness but inferior in vividness is employed as a light color ink. Moreover, a similar method has been proposed for a magenta ink (Japanese Patent Application Laid-Open No. Hei 2-127482). However, according to these methods, graininess can be improved, but a color reproduction range cannot be extended.
Generally, in a three-color ink set composed of yellow, magenta and cyan inks, and also in a four-color ink set in which a black ink is added to the three-color ink set, red color is expressed by use of the magenta ink and the yellow ink. When these two inks are used to express red color as above, sharp printing quality and good color developing properties are difficult to achieve due to a landing error of superposition. This is also the case when blue color is expressed by use of the magenta ink and the cyan ink and when green color is expressed by use of the cyan ink and the yellow ink.